Spring load system for drill string shock absorbers

ABSTRACT

A shock absorbing torque transmitting well tool is disclosed that includes an outer member and an inner member telescopically arranged. A spline means between said outer member and said inner member transmits torque. A spring means is positioned between the outer member and the inner member. The spring means includes a multiplicity of spring segments arranged in discrete spring units having different spring rates. The spring means will accommodate a wide range of loads or rapidly varying load situations. The tool operates effectively in holes started from the surface with very little weight on the bit and continues to operate effectively as the weight on the bit is increased.

United States Patent 1191 Young 5] Mar. 18, 1975 1 1 SPRING LOAD SYSTEM FOR DRILL 3,703,228 11/1972 Chana 192/109 F x STRING SHOCK ABSORBERS 3,727,902 4/1973 Burckhardt et a1 267/180 3,750,423 8/1973 Williams 64/23 [75] Inventor: James Whitehurst Young, Irving,

Tex. FOREIGN PATENTS OR APPLICATIONS Assigneez Industries, Inc. Dallas, Tex- SWltZerland Flledi C- 1973 Primary Examiner-Thomas F. Callaghan [21] Appl No: 423,964 Attorney, Agent, or FirmEddie E. Scott 52 us. c1 64/23, 175/321, 285/302, [57] ABSTRACT 403/166 A shock absorbing torque transmitting well tool is dis- [51] Int. Cl E21b 17/04 closed that includes an outer member and an inner [58] Field of Search 64/23, 15 C, 13; 175/321; member telescopically arranged. A spline means be-' 285/302; 267/166, 174, 180, 168; 403/359, tween said outer member and said inner member 166, 165, 164; 192/109 F transmits torque. A spring means is positioned bea tween the outer member and the inner member. The [56] References Cited spring means includes a multiplicity of spring seg- UNITED STATES PATENTS ments arranged in discrete spring units having differl 609 851 12/1926 Wilson 64/23 ent spring rates. The spring means will accommodate 139323000 10/1933 stake 1:11:1 "jjii:131111165351180 X a ma aaaga af laaaa a rapidly varying laaa aiaaa- 2,991'635 7/1961 warren tions. The tool operates effectively in holes started 3,180,435 4/1965 McHenry from the surface with very little weight on the bit and 3,303,894 2/1967 Varney continues to operate effectively as the weight on the 3,325,837 6/1967 Hartmann.. bit is increased. 3,345,832 10/1967 Bottoms 64/23 3,404,877 10/1968 Darnell 267/168 x 10 Clalms, 3 Drawmg Flgures PKJENTED 7 8575 3.871 .193

SHEET 1 BF 3 FIG. I

PATENTEDM 3.371.193 sum 2 m 3 FIG. 2

1 SPRING LOADSYSTEM FOR DRILL STRING SHOCK ABSORBERS BACKGROUND OF THE INVENTION The present invention relates to a drill string shock absorber adapted to be inserted in a drill string to absorb shock forces therein, and more particularly to a shock absorbing torque transmitting well too] with a spring means having separate spring units with different spring rates.

During the drilling of an oil well by the rotary method, it has become common practice to provide a section of drill collars above the drill bit. The section of drill collars provides the desired weight on the bit during drilling. The drill pipe above the section of the drill collars is generally in tension. This allows a relatively constant weight to be applied to the bit during drilling. When the hole is being started from the surface, the section of drill collars cannot be used because the length of the drill string is insufficient. A much smaller weight is therefore applied to the bit during drilling near the surface.

The action of the bit during drilling transmits shock forces to the drill string. The shock forces can be quite damaging to elements of the drill string and to drilling equipment at the surface. Drill string shock absorbers are commonly placed in the drill string to absorb the shock forces. A drill string shock absorber generally includes telescopically related parts that are separated by a spring means. The prior art shock absorbers have worked effectively with the full drilling weight on the bit. However, the prior art shock absorbers have not been effective during drilling near the surface because the weight on the bit is only a fraction of the weight on the bit at deeper depths. The spring means in the prior art shock absorbers has been too heavy to be effective during drilling near the surface. The present invention provides a drill string shock absorber that will operate effectively during drilling near the surface and will continue to operate effectively as the hole penetrates deeper into the earth.

DESCRIPTION OF PRIOR ART In U.S. Pat. No. 3,383,126 to A. H. Salvatori et al., patented May 14, 1968, a drill string shock absorber is shown. The drill string shock absorber is adapted to be inserted into a rotary drill string to absorb vibrational and shock forces therein. The shock absorber includes telescopically related parts which are separated and isolated one from the other by a mass of compressible wire material.

In U.S. Pat. No. 2,585,995 to C. C. Brown, patented Feb. 19, 1952, a drilling joint is shown. The drilling joint provides an improved means for controlling the weight applied to the drill bit, localizes the neutral point in the drill stem, and prolongs the life of the drill stem by absorbing or damping out vibrations and other shocks imparted to the drill stem during operations.

In U.S. Pat. No. 2,991,635 to F. D. Warren, patented July 1 l, 1961, a resilient drilling tool is shown. The drilling tool comprises a pair of tubular housings or pipes telescoped together and provided with cooperating splines to transmit torque from one housing to the other. A plurality of helical springs are anchored in the annulus between the two telescoped housings to constantly urge the housings in opposite directions and effectively dampen any vibration of the drill string in which the tool is interposed.

SUMMARY OF THE INVENTION The present invention provides a drill string shock absorber that will effectively act to reduce or eliminate shock forces transmitted from the bit upward through the drill string during drilling, especially during drilling with a wide range of loads on the bit or when rapidly varying load situations are encountered. The shock absorbing torque transmitting well tool of the present invention includes an outer member and an inner memher, said outer member and said inner member being telescopically arranged. Spline means are provided be-. tween said outer member and said inner member for transmitting torque. Spring means are provided connecting said outer member and said inner member. Said spring means includes a multiplicity of spring segments arranged to provide the tool with spring units having different spring rates. The above and other objects and advantages of the present invention will become apparent from a consideration of the following detailed description of the invention when taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal view, partly in section and partly in elevation, of one embodiment of a shock sub constructed in accordance with the present invention.

FIG. 2 is a view of a second embodiment of a shock sub constructed in accordance with the present invention.

FIG. 3 is a view of a portion of another embodiment ofa shock sub constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings and in particular FIG. 1, a shock sub is shown therein and generally designated by the reference number 10. The shock sub 10 is adapted to be positioned between a drill bit (not shown) and the section of the drill string that connects the drill bit to the drilling equipment at the surface. The shock sub 10 maintains a spring force coupled into the drill string assembly in such a manner that shock loads resulting from the action of the bit are absorbed and prevented from being transmitted up the drill string. The shock sub 10 minimizes fatigue on the drill bit, the drill string, and the surface equipment.

The shock sub 10 includes an upper packer sub 11. The upper packer sub 11 is adapted to be connected to the portion of the drill string extending from the surface equipment. The threaded connection 24 allows the shock sub to be easily connected to and disconnected from the drill pipe. The upper packer sub 11 is threaded into a spring sub 31 and the spring sub 31 is threaded into a spline sub 14. The spline sub 14 is threaded into a lower packer sub 20. A drive shaft mandrel 22 fits within the lower packer sub 20, the spline sub 14, the spring sub 31, and the upper packer sub 11. The drive shaft mandrel 22 includes a threaded connection 25 for connecting the drive shaft mandrel 22 to the bit. The drive shaft mandrel 22 has limited movement within the lower packer sub 20, the spline sub 14, the spring sub 31, and the upper packer sub 11. Drilling fluid is transmitted through the shock sub 10 during drilling. Drilling fluid enters the passage 26 in the upper v packer sub 11 from the section of drill string above the shock sub 10. The drilling fluid continues through a central passage in the wash pipe 12, through a central passage in the drive shaft mandrel 22, and is transmitted to the section of the drill string below the shock sub 10.

Upper packer seals 13 provide a dynamic fluid seal between the upper packer sub 11 and the drive shaft mandrel 22. Lower packer seals 21 provide a dynamic fluid seal between the lower packer sub 20 and the drive shaft mandrel 22. The enclosed area between the upper packer seals 13 and the lower packer seals 21 is filled with a lubricating oil. A ball spline 15 on the drive shaft mandrel 22 is located between the upper packer seals 13 and the lower packer seals 21. The ball spline 15 includes a series of carrier balls 16 that reduce friction and facilitate relative longitudinal movement of the drive shaft mandrel 22 and the housing consisting of the upper packer sub 11, the spring sub 31, the spline sub 14, and the lower packer sub 20. A ball spline 17 is positioned between the drive shaft mandrel 22 and the spline sub 14 to transmit torque from the housing consisting of the upper packer sub 11, the spring sub 31, the spline sub 14, and the lower packer sub 20. The ball spline 17 includes a series of carrier balls 18 that transmit between spline grooves 27 connected to the drive shaft mandrel 22 and spline grooves 19 connected to the spline sub 14.

An upper spring unit 28 and a lower spring unit 29 are positioned between the upper packer sub 11 and the drive shaft mandrel 22. The spring units 28 and 29 absorb the shock loads resulting from the action of the bit. The upper spring unit 28 consists of six disc or Belleville springs 30. The lower spring unit 29 consists of two disc or Belleville springs 30. This arrangement allows the initial spring rate to be governed largely by the spring unit 29 until these springs have deflected to the point that they are completely bottomed out. At this time the heavier or stronger spring unit 28 will have deflected in proportion to the imposed load and will now dominate the effective spring rate. During drilling near the surface, the weight on the bit is small compared to the weight on the bit during drilling at deeper depths. During drilling near the surface, the spring unit 29 will deflect and absorb shock forces produced by the action of the bit. As the hole penetrates deeper into the earth, the spring unit 28 will dominate and the shock forces produced by the action of the bit will be absorbed. The shock forces resulting from action of the bit are also absorbed by a swabbing or damping action brought about by restricting the escape of the lubricant trapped between the springs 30. The geometry of the spring allows them to reduce in ID. and expand in CD. as loads are applied. Lubricant is trapped to some degree as the springs are collapsed providing a damping effect and the shock forces are absorbed. The degree of damping action can be controlled by the oil viscosity, clearance grooves, and spring geometry.

Referring now to FIG. 2, another embodiment of a shock sub constructed in accordance with the present invention is shown. The shock sub is generally designated by the reference number 48. The shock sub 48 is adapted to be positioned between a drill bit (not shown) and the section of drill string that connects the drill bit to the drilling equipment at the surface. The shock sub 48 contains a spring force coupled into the drill string assembly in such a manner that shock loads resulting from the action of the bit are absorbed and prevented from being transmitted up the drill string. The shock sub 48 minimizes fatigue on the drill bit, the drill string, and the surface equipment.

The shock sub 48 includes an upper packer sub 49. The upper packer sub 49 is adapted to be connected to the portion of the drill string extending from the surface equipment. The threaded connection 41 allows the shock sub 48 to be easily connected to and disconnected from the drill pipe. The upper packer sub 49 is threaded into a spline sub 32 and the spline sub 32 is threaded into a lower packer sub 38. A drive shaft mandrel fits within the lower packer sub 38, the spline sub 32, and the upper packer sub 49. The-drive shaft mandrel 40 includes a threaded connection 42 for connecting the shock sub 48 to that portion of the drill string connected to the bit. The drive shaft mandrel 40 has limited movement within the lower packer sub 38, the spline sub 32, and the upper packer sub 49. Drilling fluid is transmitted through the shock sub 48 during drilling. Drilling fluid enters the passage 43 in the upper packer sub 49 from the section of the drill string above the shock sub 48. The drilling fluid continues through a central passage in the wash pipe 50, through a central passage in the drive shaft mandrel 40, and is transmitted to the section of the drill string below the shock sub 48.

Upper packer seals 51 provide a dynamic fluid seal between the'upper packer sub 48 and the drive shaft mandrel 40. Lower packer seals 39 provide a dynamic fluid seal between the lower packer sub 38 and the drive shaft mandrel 40. The enclosed area between the upper packer seals 51 and the lower packer seals 39 is filled with a lubricating oil. A ball spline 33 on the drive shaft mandrel 40 is located between the upper packer seals 51 and the lower packer seals 39. The ball spline 51 includes a series of carrier balls 34 that reduce friction and facilitate relative longitudinal movement of the drive shaft mandrel 40 and the housing consisting of the upper packer sub 49, the spline sub 32, and the lower packer sub 38. A ball spline 35 is positioned between the drive shaft mandrel 40 and the spline sub 32 to transmit torque from the housing consisting of the upper packer sub 49, the spline sub 32, and the lower packer sub 38. The ball spline 35 includes a series of carrier balls 36 that transmit torque between spline grooves 47 connected to the drive shaft mandrel 40 and spline grooves 37 connected to the spline sub 32.

Springs 44 and 45 are positioned between the upper packer sub 49 and the drive shaft mandrel 40. A divider 46 connects springs 44 and 45. The springs 44 and 45 absorb the shock load resulting from the action of the bit. The cross-sectional area of spring 45 is less than the cross-sectional area of spring 44. The combination of springs 44 and 45 provides a progressive increase in spring rate. This arrangement allows for the initial spring rate to be governed largely by the weaker spring 45 until spring 45 has deflected to the point that it is completely bottomed out on divider 46. At that time the heavier'spring 44 has been deflected in proportion to the imposed load and will now dominate the effective spring rate. This insures that the shock sub 28 will operate effectively during drilling near the surface and continue to operate effectively as the hole penetrates deeper into the earth.

Referring now to FIG. 3, a portion of another embodiment of a shock sub constructed in accordance with the present invention is shown. The shock sub is generally designated by the reference number 52. The shock sub 52 is adapted to be positioned between a drill bit (not shown) and the section of drill string that connects the drill bit to the drilling equipment at the surface. The shock sub 52 contains a spring force coupled into the drill string assembly in such a manner that shock loads resulting from the action of the bit are absorbed and prevented from being transmitted up the drill string. The shock sub 52 minimizes fatigue on the drill bit, the drill string, and the surface equipment.

The shock sub 52 includes an upper packer sub 53. The upper packer sub 53 is adapted to be connected to the portion of the drill string extending from the surface equipment. The upper packer sub 53 is threaded into a spline sub 54. A drive shaft mandrel 55 fits within the spline sub 54 and the upper packer sub 53. The drive shaft mandrel 55 includes a threaded connection (not shown) for connecting the shock sub 52 to that portion of the drill string connected to the bit. The drive shaft mandrel 55 has limited movement within the spline sub 54, and the upper packer sub 53. Drilling fluid is transmitted through the shock sub 52 during drilling. Drilling fluid enters a passage in the upper packer sub 53 from the section of the drill string above the shock sub 52. The drilling fluid continues through a central passage in the drive shaft mandrel 55 and is transmitted to the section of the drill string below the shock sub 52.

Upper packer seals 56 provide a dynamic fluid seal between the upper packer sub 53 and the drive shaft mandrel 55. Lower packer seals (not shown) provide a dynamic fluid seal between a lower packer sub (not shown) connected to spline sub 54 and the drive shaft mandrel 55. The enclosed area between the upper packer seals 56 and the lower packer seals is filled with a lubricating oil. A ball spline 57 on the drive shaft mandrel 55 is located between the upper packer seals 56 and the lower packer seals. The ball spline 57 includes a series of carrier balls 58 that reduce friction and facilitate relative longitudinal movement of the drive shaft mandrel 55 and the housing consisting of the upper packer sub 53, the spline sub 54, and the lower packer sub. A ball spline 59 is positioned between the drive shaft mandrel 55 and the spline sub 54 to transmit torque from the housing consisting of the upper packer sub 53, the spline sub 54, and the lower packer sub. The ball spline 59 includes a series of carrier balls 60 that transmit torque between spline grooves 61 connected to the drive shaft mandrel 55 and the spline grooves 62 connected to the spline sub 54.

Spring units 63, 64, and 65 are positioned between the upper packer sub 53 and the drive shaft mandrel 55. The spring units 63, 64, and 65 absorb the shock loads resulting from the action of the bit. The spring units 63, 64, and 65 consist of a multiplicity of disc or Belleville springs 66 arranged in various combinations of series and parallel stacking. Spring unit 63 consists of two sets of six disc or Belleville springs 66. Spring unit 64 consists of two sets of four disc or Belleville spring 66 and spring unit 65 consists of two sets of two disc or Belleville springs 66. This arrangement allows for the initial spring rate to be governed largely by the lesser spring unit 65 until these springs have deflected to the point that they are completely bottomed out on the stops 67. At that time the adjacent and heavier spring unit 64 will have deflected in proportion to the imposed load and will now dominate the effective spring rate. This will continue until the springs 66 making up spring unit 64 have deflected to the point where they are completely bottomed out on the stops 67. At that time the adjacent and heavier spring unit 63 will have been deflected in proportion to the imposed load and will now dominate the effective spring rate. The spring units 63, 64, and 65 will therefore accommodate a great variety of effective loads and degrees of deflectlon.

A swabbing or damping action is provided by restricting the escape of lubricant trapped between the Belleville springs 66. The geometry of the springs allows them to reduce in ID. and expand in CD. as loads are applied. Lubricant is trapped to some degree as the springs are collapsed and the shock loads are absorbed. The oil viscosity, clearance grooves, and spring geometry can be used to control the damping action. The shock sub 52 will operate effectively during drilling near the surface and continue to operate effectively as the hole penetrates deeper into the earth and greater weight is applied to the bit.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A shock absorbing torque transmitting well tool. comprising:

an outer member;

an inner member, said outer member and said inner member being telescopically arranged;

spline means between said outer member and said inner member for transmitting torque; and

spring means connected to said outer member and connected to said inner member, said spring means including a first spring unit with a first spring constant and a second spring unit with a second and different spring constant said first spring unit and said second spring unit including a multiplicity of disc springs positioned between said inner and outer members.

2. The shock absorbing torque transmitting well tool of claim 1 including stop elements connected to said disc springs.

3. The shock absorbing torque transmitting well tool of claim 2 wherein the stop elements are annular elements positioned between matching disc elements.

4. The shock absorbing torque transmitting well tool of claim 3 including oil positioned between said inner and outer member wherein the clearance between said disc springs and said inner and outer members restricts the passage of said oil.

5. A shock absorbing torque transmitting well tool, comprising:

an outer member;

an inner member, said outer member and said inner member being telescopically arranged;

spline means between said outer member and said inner member for transmitting torque; and

spring means connected with said outer member and connected with said inner member, said spring means including a first spring unit with a multiplicity of disc spring elements and a second spring unit with a second and different multiplicity of disc spring elements.

6. The shock absorbing torque transmitting well too] of claim including a fluid between said innermember and said outer member with the disc spring elements positioned between said inner member and said outer member to restrict passage of said fluid.

7. The shock absorbing torque transmitting well tool of claim 6 including stop elements positioned within said disc spring elements.

8. A shock absorbing torque transmitting well tool, comprising:

an outer member;

an inner member, said outer member and said inner member being telescopically arranged;

an upper seal between said outer member and said inner member;

a lower seal between said outer member and said inner member;

a fluid between said upper seal and said lower seal;

spline means between said outer member and said inner member for transmitting torque; and

spring means connected with said outer member and connected with said inner member with said spring means including a first multiplicity of disc spring units and a second multiplicity of disc spring units, said first multiplicity of disc spring units being a different number of disc spring units than said second multiplicity of disc spring units.

9. The shock absorbing torque transmitting well tool of claim 8 wherein said first and second multiplicity of disc spring units are positioned between said outer member and said inner member to restrict passage of said fluid.

10. The shock absorbing torque transmitting well tool of claim 9 including stop elements within said disc 

1. A shock absorbing torque transmitting well tool, comprising: an outer member; an inner member, said outer member and said inner member being telescopically arranged; spline means between said outer member and said inner member for transmitting torque; and spring means connected to said outer member and connected to said inner member, said spring means including a first spring unit with a first spring constant and a second spring unit with a second and different spring constant said first spring unit and said second spring unit including a multiplicity of disc springs positioned between said inner and outer members.
 2. The shock absorbing torque transmitting well tool of claim 1 including stop elements connected to said disc springs.
 3. The shock absorbing torque transmitting well tool of claim 2 wherein the stop elements are annular elements positioned between matching disc elements.
 4. The shock absorbing torque transmitting well tool of claim 3 including oil positioned between said inner and outer member wherein the clearance between said disc springs and said inner and outer members restricts the passage of said oil.
 5. A shock absorbing torque transmitting well tool, comprising: an outer member; an inner member, said outer member and said inner member being telescopically arranged; spline means between said outer member and said inner member for transmitting torque; and spring means connected with said outer member and connected with said inner member, said spring means including a first spring unit with a multiplicity of disc spring elements and a second spring unit with a second and different multiplicity of disc spring elements.
 6. The shock absorbing torque transmitting well tool of claim 5 including a fluid between said inner member and said outer member with the disc spring elements positioned between said inner member and said outer member to restrict passage of said fluid.
 7. The shock absorbing torque transmitting well tool of claim 6 including stop elements positioned within said disc spring elements.
 8. A shock absorbing torque transmitting well tool, comprising: an outer member; an inner member, said outer member and said inner member being telescopically arranged; an upper seal between said outer member and said inner member; a lower seal between said outer member and said inner member; a fluid between said upper seal and said lower seal; spline means between said outer member and said inner member for transmitting torque; and spring means connected with said outer member and connected with said inner member with said spring means including a first multiplicity of disc spring units and a second multiplicity of disc spring units, said first multiplicity of disc spring units being a different number of disc spring units than said second multiplicity of disc spring units.
 9. The shock absorbing torque transmitting well tool of claim 8 wherein said first and second multiplicity of disc spring units are positioned between said outer member and said inner member to restrict passage of said fluid.
 10. The shock absorbing torque transmitting well tool of claim 9 including stop elements within said disc spring units. 